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University of Nairobi (2012)

Breeding Maize for early maturity and drought tolerance in Kenya using anthesis to silking interval

Juma, Ongeti C

Titre : Breeding Maize for early maturity and drought tolerance in Kenya using anthesis to silking interval

Auteur : Juma, Ongeti C

Université de soutenance : University of Nairobi

Grade : Master of Science (MS) 2012

Résumé
Maize is the most important staple crop grown in all the agro-ecological zones of Kenya including the Arid and semi-arid lands (ASALs) that cover 80% of the total land mass. Due to climate change prevalent globally, an increase in rainfall variance will lead most of the times to frequent droughts in Kenya‘s dry-lands. In this study, one hundred and thirty five F2 ;F3 progenies developed from crosses between long ASI, Katumani composites and short ASI, elite CIMMYT genotypes were evaluated alongside five checks (Duma 43 Hybrid, Local Katumani composite, CML440/CML445, CML312/CML442 and P100C6/CML78) under drought stressed and well-watered environments, at the Kiboko sub-station of KARI during 2011 and 2012 seasons in an alpha lattice design with three replications. The results showed that the genotypic, environmental, and genotype x environment (G x E) interaction variances were all significant under drought stress. The G x E variance for ASI was greater than the genotypic variance under water stress whereas for grain yield the G x E variance was almost similar to the genotypic variance. Under drought stress, the ASI mean increased significantly up to 7.667 days from an average of 1.6 days under well watered environment. Days to maturity, under drought stress decreased to an average of 53 days compared to an average of 57days under well watered conditions for all the genotypes. The mean grain yield (GY) decreased significantly by an average of 78.02% under drought stress. The G x E interactions contributed largely to the variations in performance across the two contrasting environments. The high yielding early- maturing genotypes (KDV2/CML444-14, and KDV2/CML440-224) under drought stress were alsohigh yielding under well watered environments. xii Anthesis to silking interval (ASI) was significantly negatively correlated with GY (-0.446***) under stress but not under well watered conditions. The ASI was positively significantly correlated with stress susceptible index (SSI)(0.304***), leaf rolling (LR)- (0.219**), senescence (SEN) (0.153*) but ASI was negatively significantly correlated with stress tolerance index (STI) (-0.378***), geometric mean productivity (GMP) (-0.448***), mean productivity (MP) (-0.419***), yield stress index (YSI) (-0.303***) and water use efficiency (WUE) (-0.365***). These relationships confirmed that ASI is important for use in selection under drought stressed environments. Genotypes with a high WUE index under drought stress had a higher chance of having a shorter ASI. Similarly, such genotypes with a high WUE index under drought stress had a higher chance of being high yielding. F3 ; F4 genotypes KDV2/CML444-14, and KDV2/CML440-224 were early maturing, had a short ASI, a high WUE index and were high yielding under drought stressed environments. On the other hand, grain yield under drought stress was positively, significantly correlated with MP (0.819 ***), GMP (0.961***), STI (0.890***), WUE (0.581***) and YSI (0.739***) under drought stressed environment. It is therefore concluded that in breeding maize for drought tolerance, consideration should be given to establishing carefully managed drought stress environments. Under such environments, ASI, earliness, WUE and computed drought indices are important secondary selection parameters. In this study it was proven that it is possible to combine both drought escaping mechanisms such as earliness and drought tolerance mechanisms such as ASI in developing high yielding, early maturing drought tolerant maize for ASALs in Kenya

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